Definition 3.9 [1]}
Given \(\mathcal {A} \in T_{m,n}\)  and \(R_i(\mathcal {A})= (r_{i i_2 ...i_m })_{i_2 ...i_m}^n \in T_{m-1,n}\)  such that \(r_{i i_2 ... i_m} = a_{i i_2 ...i_m} \) , then \(\mathcal {A}\)  is called row subtensor diagonal, or simply row diagonal, if all its row subtensor \(R_i(\mathcal {A}), \; i=1,2,...,n\)  are diagonal tensors, namely, if \(a_{i i_2 ...i_m}\)  can take nonzero values only when \(i_2 = \cdot \cdot \cdot = i_m\) .

